This invention relates to a process and device for analysis of roller bearings installed in machines, a sensor recording the signal which is produced by the motion of the rolling element and the signal amplitude being evaluated in order to determine the presence and optionally the depth of damage in the roller bearing running surface.
Damage on the running surface of roller bearing rings in bearing operation each time a rolling element rolls over the damage site leads to excitation of vibration of the roller bearing and the machine components which are mechanically coupled to it. Here, conventionally by means of an acceleration transducer which is coupled for example to a bearing block, an acceleration signal is determined which results from the deflection or the absorption of force of the rolling element at the damage site. For diagnosis of the roller bearing state especially the depth of existing damage is of interest.
A survey of vibration-diagnostic methods for roller bearings is known from section 6.1 of Vibration-diagnostic Assessment of Machines and Systems by Ulrich Klein, published by the Association for Operating Strength Research, Steel-Iron Publishing House, Duesseldorf, 1998. It describes for example transducer resonance techniques, the sensor signal being subjected to bandpass filtration around the resonant frequency of the sensor. In impact-pulse measurement the average value of the sensor signal is found, while in the SEE method the time derivative of the acceleration is formed and its intensity in the range of high frequencies up to 300 kHz is analyzed. In the spike energy method the bandpass-limited acceleration average, the envelope curve of the alternating amplitudes and the peak value relative to the effective value are analyzed, the results being evaluated by means of empirically determined normalization to the rpm and the bearing diameter. The defect in this method is that damage on the inner ring can hardly be detected and furthermore for certain types of machines, normalization is not appropriate. Furthermore, the indicated book describes processes in which the peak holding capacity of the amplitude distribution and the statistical distribution are evaluated.
Furthermore, for normalization of the acceleration signal amplitude after envelope curve formation in the time domain, the attempt was made to draw conclusions regarding the transfer function of damage excitation from the structure resonances or the tone frequencies of the bearing components. This process however did not deliver satisfactory results since the structure resonances or tone frequencies of the bearing components in the unclamped state hardly allow conclusions regarding the transfer behavior of the installed bearing.
Other examples for evaluation of the envelope curve signal in the time domain can be found in U.S. Pat. No. 4,007,630 and U.S. Pat. No. 3,554,012.
The object of this invention is to devise a process and device for analysis of roller bearings in machines, by means of which conclusions regarding the depth of damage in a roller bearing running surface are reliably possible from the signal amplitude.
This object is achieved as claimed in the invention by a process as claimed in claim 1 and a device as claimed in claim 32.
In the approach as claimed in the invention it is advantageous that realistic normalization of the signal amplitude is enabled by at least approximate determination of the transfer function so that reliable evaluation of the damage depth is enabled.
Preferred embodiments of the invention follow from the dependent claims.